Abstract
Virulence of bovid herpesvirus 1 (BHV-1) for C57BL suckling mice was compared among respiratory, genital and attenuated vaccine strains. The 50% mouse lethal dose of the respiratory strain was approximately 1, 000-fold lower than that of the vaccine strain. The genital strain showed intermediate virulence. The kinetic studies suggested that the respiratory strain appeared to multiply in the brain of the animals, and that the genital and vaccine strains were eradicated from the animals.